The Collaborative International Dictionary of English v.0.48:

Divining \Di*vin"ing\, a.
   That divines; for divining.
   [1913 Webster]

   Divining rod, a rod, commonly of witch hazel, with forked
      branches, used by those who claim to be able to discover
      water or metals under ground by sensing them through such
      a rod.
      [1913 Webster]

WordNet (r) 3.0 (2006):

divining rod
    n 1: forked stick that is said to dip down to indicate
         underground water or oil [syn: divining rod, dowser,
         dowsing rod, waterfinder, water finder]